US3798840A

US3798840A - Grinding machine with a cam-controlled dressing apparatus

Info

Publication number: US3798840A
Application number: US00244132A
Authority: US
Inventors: E Robillard; H Uhtenwoltd
Original assignee: Cincinnati Milacron Heald Corp
Current assignee: Cincinnati Milacron Heald Corp
Priority date: 1972-04-14
Filing date: 1972-04-14
Publication date: 1974-03-26
Anticipated expiration: 1991-03-26
Also published as: JPS5216839B2; DE2319263A1; JPS4920790A; GB1414718A

Abstract

A grinding machine having a dressing apparatus which makes use of a master cam for producing a desired shape on an abrasive wheel.

Description

United States Patent [191 Robillard et al.

[4 1 Mar. 26, 1974 GRINDING MACHINE WITH A [56] References Cited CAM-CONTROLLED DRESSING UNITED STATES PATENTS APPARATUS 2,862,493 12/1958 Pesce 125/11 TP Inventors; Edward George Robillard, Cherry 3,403,480 10/1968 Robillard 5l/165.87 v Herbert Rudolph 3,605,344 9/1971 Hahn et a1. 51/165.8 X Uhtenwoltd, Worcester, both of 3,612,031 10/1971 Mazzarelh 125/11 CC Mass- FOREIGN PATENTS OR APPLICATIONS Assignee: Cincinnati Milacron-Heald Corp., 1,196,778 0/1959 France 125/11 TP Worcester, Mass.

Primary Examiner-Othell M. Simpson Flled' Apr. 1972 Assistant ExaminerNicho1as P. Godici Appl- N -I 244,132 Attorney, Agent, or Firm-Norman S. Blodgett; Gerry A. Blodgett U.S. C1 51/5, 51/165.87, 51/165.93,

125/11 CC [57] ABSTRACT Int. Cl 1324b 53/08 A grinding machine having a dressing apparatus which Fleld of Search 51/165.8, 165.84, 165.87, makes use of a master Cam for producing a desired 51/165.78, 165.79, 165.89, 2 F, 165.93, 5, Shape on an abrasive wheeL 129,131;125/11TP,11PH,11CC

6 Claims, 9 Drawing Figures CONTROL BOX PATENTEDMARZS I974 SHEET 2 OF 6 FIG. 3

FIG. 4

FIG. 5

PATENTED MARZS I974 SHEET R [If 6 STD.

COMPENSAT- ION "COARSE COMPENSAT- ION IF USED) I ION (IF USED) AUX. COMPENSAT- ION (IF USED) RE TRACTION AUX. COMPENSA T- INSTALL JUMPER FOR IOO STEP/SEC MODE "IJ Q 0 mm n W& 7 wWM eE m 0 w 4mm 8 42 I M fiqmmmmm v nnnn nn xssssfiss RET COMM.

STD. COMP COMM.

OARSE COMF. COMM.

AUX RE T. COMM.

AUX. COMP COMM.

DEC. RATE 2 MEG. MAX.

Pmmmmzs m4 1798,8 10

SHEET 5 [If 6 MOTOR DRIVE a PULSE TO STEP CONVERTER SPARE 87 PULSE GENERATOR LOGIC a5- ac. D. DOWN COUNTER 84 5.0.0. DOWN COUNTER 83 PULSER 82\ COUNT LOGIC SPARE 8/ INPUT INTERFACE SPARE BLANK 12 v. 0. C. REGULATOR CARD CAGE FOR INTEGRATED CIRCUIT COMPENSATOR UN/T FIG. 7

GRINDING MACHINE WITH A CAM-CONTROLLED DRESSING APPARATUS BACKGROUND OF THE INVENTION There are many situations in the manufacture of machinery where it is desirable to use a non-cylindrical surface of revolution and it is desirable to finish this surface by the grinding method. It has been proposed that this be done by the plunge-grinding method after the abrasive wheel has been dressed in exact duplication of the cross-sectional shape of the surface to be generated. The apparatus that has evolved over the years consists of equipment for passing the abrasive wheel longitudinally along its axis past the diamond, while moving the diamond transversely by means, for instance, of a cam bolted on the rear of the wheelhead table which carries the abrasive wheel. While this type of construction is adequate for some purposes, it does not give the accuracy necessary in many applications. For instance, it is common practice to produce a crowned surface on the groove of the race of of a roller bearing. This race must have not only a very smooth surface, but the shape of the curve is critical to proper operation of the bearing. The type of grinding apparatus described above simply does not produce the desired accuracy of tolerance of geometric shape desirable in such a grinding application. Furthermore, it does not lend itself to grinding operations in which other surfaces are combined with the aforementioned curve surface, including those grinding operations where facing is accomplished as part of the same grinding cycle as the plunge-grinding of the curved surface. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the invention to provide a grinding machine providing means for producing a very accurately-shaped abrasive wheel.

Another object of this invention is the provision of a grinding machine having means for dressing an abrasive wheel very accurately for plunge-grinding ofa noncylindrical surface.

A further object of the present invention is the provision of a grinding machine capable of performing in a single grinding cycle the formation of accuratelyformed, non-cylindrical surfaces as well as cylindrical surfaces and flat radial surfaces.

It is another object of the instant invention to provide a grinding machine having a contour dressing apparatus in which small inaccuracies in the master cam pro duce negligible errors in the dressed wheel.

A still further object of the invention is the provision of a grinding machine in which grinding is accomplished not only with a surface of revolution which is concentric with the wheel axis, but also with a radial surface; provision is made for dressing both surfaces with accompanying separate compensation.

It is a further object of the invention to provide a grinding machine having a contour dressing capability in which movement of the dressing apparatus is brought about accurately by use of electronic circuitry composed of solid state elements, logic circuitry, and readily-replaceable printed circuit boards.

It is a still further object of the present invention tp provide a grinding machine capable of performing facing operations and accurately-formed surfaces of revolution in the same grinding cycle.

With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

SUMMARY OF THE INVENTION In general, the invention consists of a grinding machine for generating a surface of revolution on a workpiece by the abrasive method and having a base, having a workhead mounted on the base and adapted to support and rotate the workpiece about the axis of the said surface of revolution, and having a wheelhead mounted on the base and having a rotatable spindle carrying an abrasive wheel. Means is provided for producing relative movement between the wheelhead and the workhead in directions parallel to the said axis and transversely of the axis to produce a grinding cycle. The dressing apparatus is associated with the base and means is provided for producing relative movement between the dressing apparatus and the wheelhead both transversely of the axis and longitudinally of the axis to generate a duplicate of the said surface of revolution on the surface of the wheel.

More specifically, a master cam is associated with the apparatus, which master cam duplicates a generatrix of the said surface of revolution. Means is provided for connecting the master cam to the dressing apparatus and the wheelhead so that the displacement from point to point of the dressing apparatus over the abrasive wheel is substantially less than the corresponding displacement on the master cam. A pulse generator is moved over the master cam and produces pulses proportional in number to the displacement of the surface of the cam from a reference plane; the transverse movement between the dressing apparatus and the wheelhead is brought about by the use of a stepping motor receiving the pulses from the pulse generator.

BRIEF DESCRIPTION OF THE DRAWINGS The character of the invention, however, may be best understood by reference to one of its structural forms, as illustrated by the accompanying drawings, in which:

FIG. 1 is a plan view somewhat schematic in nature of a grinding machine embodying the principles of the present invention,

FIG. 2 is an enlarged sectional view of a workpiece and abrasive wheel illustrating the use of the machine,

FIG. 3 is a vertical sectional view of a portion of the machine taken on the line III-III of FIG. 1,

FIG. 4 is a plan view of a dressing apparatus forming part of the machine,

FIG. 5 is a side elevational view of the dressing apparatus,

FIGS. 6A and 6B are schematic electrical diagrams of the controls associated with the machine,

FIG. 7 is a diagram showing the relationship of various parts of the control apparatus, and

FIG. 8 is a detailed electrical diagram of a pulse generator logic board forming part of the control appara- DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1, wherein are best shown the general features of the invention, the grinding machine, indicated generally by the reference numeral 10, is

shown as an internal grinding machine of the type shown in the U.S. Pat. of Edward G. Robillard No. 3,601,930 which issued Aug. 31, 1971. The machine is provided with a base 1 1 having an upper horizontal surface on which are mounted a workhead table 12 and a wheelhead table 13. The workhead table 12 is mounted on

ways

14 and 15, so that it slides longitudinally of the base. The wheelhead table 13 is mounted on

ways

16 and 17, so that it slides transversely of the base. A hydraulic cylinder 18 serves to move the table 12 along its

ways

14 and 15, while a hydraulic cylinder 19 serves to move the table 13 along its

ways

16 and 17. Mounted on the workhead table 12 is a workhead 21 having mounted in it a rotatable spindle 22 driven by an electric motor 23. The end of the spindle 22 not connected to the motor 23 extends from the workhead and is provided with a platen 24 which contacts a radial end surface of a workpiece 25 which is also supported by shoes 26. Mounted on the side of the table 12 adjacent the table 13 is a dressing apparatus 27. Mounted at the front of the table 12 is a master cam 28 having an operative surface 29 having the general configuration of a generatrix ofa surface of revolution which is to be generated.

The wheelhead table 13 has mounted on its upper surface a wheelhead 31 having a self-contained motor for rotating a spindle 32 which carries an abrasive wheel 33 at its outer end. The underside of the table 13 is provided with a nut 34 which is engaged by a balltype feed screw 35 driven by a stepping motor 36 through a gear reduction unit 37.

Mounted on the base 11 adjacent the cam 28 is a rotary pulse generator 38 having a vertical input shaft 39 extending upwardly and having keyed to it an actuating arm 41. The arm 41 is biased in a counter-clockwise direction by a coil spring 42. Its outer end is connected to a transversely-sliding cam follower 43. The pulse generator 38 is of the dual-channel rotary pulse type generator Model 989 04.asst dauntin tured by Trump- Ros lndustrial Controls, Inc. of North Billerica, Massachusetts. The generator converts shaft rotation into two channels of square wave outputs. The transitions give information on the exact position of the shaft, while the phase relation of the channels indicates direction. The square wave signals in the channels are produced internally of the generator by the use of a lamp and photocell arrangement. The output of the generator is connected by a cable 44 to a control box 45 which, in turn, is connected by a cable 46 to the stepping motor 36.

The machine is provided with the usual hydraulic controls for regulating the operation of the

hydraulic cylinders

18 and 19 and with the usual switches and the like which are connected to the control box 45 for the operation of the grinding machine to produce grinding cycles. Basically, the

cylinders

18 and 19 serve to move the workhead table 12 and the wheelhead table 13 longitudinally and transversely relative to one another to bring about a selected grinding cycle. In addition, the movement of the table 12 relative to the base 11 in a longitudinal direction is supplemented by the use of a stepping motor 47 mounted on an extension 48 of the base. An extension 49 of the table 12 overlies the extension 48 and between the two rests a table 51, which will be described more fully hereinafter.

In FIG. 2, it can be seen that the workpiece 25 is shown as being the cup of a roller bearing. As such, it has a surface of revolution 52 which is to be finished as well as a radial surface 53 on the bottom of the cup. The workpiece 25 has an outer radial surface 54 which is engaged by the platen 24 of the workhead and an outer cylindrical surface 55 which is engaged by the shoes 26 for the support of the workpiece during grinding. It is desirable in the production of a roller bearing to make the surface 52 slightly curved toward the middle, as shown in exaggerated form in the drawing. The abrasive wheel 33 is provided with a radial end surface 56 for engaging and finishing the radial surface 53 of the workpiece and with a surface of revolution 57 which has the shape of the surface 52 of the workpiece to be finished. Grinding is done by plunge operations, a longitudinal plunge of the spindle 33 taking place to bring the surface 56 of the wheel into engagement with the surface 53 of the workpiece and to finish it. The wheel is then withdrawn from the cup until it is coextensive with the surface 52 and it is plunged radially to accomplish the formation and finishing of the surface 52.

In FIG. 3 it can be seen that the cylinder 18 is connected between the table 12 and the table 51, while the motor 47 is connected by a gear reduction unit to a screw 58 which operates on a nut 59 mounted on the table 51. In other words, the motor 47 and its associated equipment connect the base 11 to the table 51, which is mounted on the extension 48 of the base for sliding motion longitudinally thereof. Suitable switches and dogs are mounted on the extension 44 of the table 12 and on the upper part of the table 15 to give signals to the control box when various positions of the table 12 are reached.

FIGS. 4 and 5 show the details of the dressing apparatus 27. The base 61 is fastened to the table 12 and to this is hinged an arm 62 carrying a diamond 63 at its forward end. The arm 62 is pivoted about a horizontal axis by means of a hydraulic cylinder 64 and a switch 65 is engaged by stops on the arm 62 to indicate when operative and inoperative positions are reached at the end of the swing. Also attached to the arm 62 is another arm 66 carrying a facing diamond 67.

Cylinders

68 and 69 are built into the arm 62 to cause the arm 66 to rotate relative to it and suitable switches are provided indicating the up" and down positions of the arm 66 relative to the arm 62.

Referring to FIGS. 6a and 6b, it can be seen that they constitute a schematic showing of the interior of the control box 45. In general the controls are similar to those shown in the US. Pat. of Robillard No. 3,403,480 which issued on Oct. 1, 1968, and the patent application of Edward G. Robillard et al, Ser. No. 879,785 filed Nov. 25, 1969, now US. Pat. No. 3,634,979. The rotary pulse generator 38 is connected to an integrated circuit compensator unit 71 by fine lines enclosed in the cable 44. The stepping motor 36 is connected with a cable 46 to the unit 71, as is a 24-volt DC power supply 72. The cable 73 connects to the unit 71 a series of digital switches, including a switch 73 for standard compensation, a switch 74 which can be set for coarse compensation, a switch 75 for retraction, a switch 75 for auxiliary retraction, and a switch 77 for auxiliary compensation. A cable 78 includes lines connecting the power supply 72 to the unit as well as numerous machine control switches.

In FIG. 7 is shown a physical picture of the unit 71 with the

cables

44, 73, 46 and 78 extending from it. Mounted on the surface of the unit are various solid state electronic cards carrying some of the largest portions of the control apparatus. The details of these cards are shown in the aforementioned U.S. Pat. No. 3,634,979 of Robillard. For instance, card 79 is a 12- volt DC regulator shown in FIG. 13 of the US. Pat. No. 3,634,979, a card 81 is similar to the input interface shown in FIG. 32 of the application, card 82 is a count logic card as shown in FIG. 28 of the application, and a card 83 is a pulser shown in FIG. 27 of the application.

Cards

84 and 85 represent a B.C.D. down counter shown in FIG. 26 of the application and a card 86 represents the motor driver and the pulse-to-step converter shown in FIGS. 24 and 25 of the patent application. The pulse generator logic card 87 is shown in FIG. 8 of the present application.

In FIG. 8 it can be seen that the pulse generator logic board 87 has a plurality of gate transistors 88 through 117 which operate as hand gates to transfer the pulses from the rotary pulse generator 38 to the stepping motor 36. Most importantly, the input side of the transistor 88 is connected by a line 118, forming part of the cable as connected to channel 8 of the pulse generator. Similarly, the transistor 90 is connected by a line 119 to channel A of the generator. At the output side of the logic board the line 120 leads from the transistor 112 to the front binding post on the stepping motor 36, while a line 121 leads from the output of the transistor 113 to the rear binding post of the motor 36. The purpose of the logic board 87 is to determine the rate in which pulses are passed from the pulse generator 38 to the stepping motor 36 and the direction that the motor is to take. The circuitry includes the ONE-SHOT

gates

122 and 123, as well as an output line 124 which carries a steady stream of pulses.

The operation of the invention will now be readily understood in view of the above description. With the motor 23 driving the workhead 21 and the wheelhead 31 energized, the abrasive wheel 33 rotates about its axis and the workpiece 25 is also rotated about the axis of the surface 52 which is to be generated. The control operating the

cylinders

18 and 19 causes the table 12 to move to the right with the abrasive wheel 33 located practically concentrically with the surface 52 of the workpiece. The movement continues until the wheel 33 engages the workpiece with its radial surface 56 contacting the radial surface 53 of the workpiece, thus finishing that surface. Next, a longitudinal motion of the table 12 is brought about by energization of the stepping motor 47', thus causing it to move to the right until the surface 57 of the abrasive wheel 33 is co-extensive with the surface 52 of the workpiece which is to be ground. A plunge grind takes place by the energization of the cross-feed cylinder 19. This plunge operation is finished, the wheel is backed off by energization of the cylinder 19, and the forward motion of the table 13 takes place until the wheel is again centered with the workpiece. The workhead tablecylinder 18- is energized again, thus carrying the workpiece away from thewheel and'the diamond past the wheel to retracted position in FIG. 1. At that time, the loading of a new workpiece takes place.

In the process of passing the diamond 63 longitudinally past the wheel 33, however, table 13 is moved rearwardly in a particular pattern so that the diamond 63 (which has been moved into its down" position) generates a desired geometric shape on the surface 57 of the wheel 33. The manner in which this is done is that the cam 28, as the table 12 moves to the left, engages the cam follow 43 and brings about the rotation of the shaft 39 of the pulse generator through the medium of the crank arm 41. As the table 12 moves to the left, the cam follower 43 follows the shape of the surface 29 of the cam and the shaft 39 is similarly rotated. This generates pulses in the cable 44 which is connected to the box 45. This, in turn, converts those pulses and passes them through the cable 46 to the stepping motor 36. The stepping motor 36 rotates through the gear reduction unit 37, causing a rotation of the ball screw 35 and bringing about transverse motion of the wheelhead table 13 in accordance with pulses generated by the generator 38. The pulses are in forward or rear mode in accordance with the direction the cam follow 43 is moving as it slides over the surface 29 of the cam 28.

When it is desirable to dress the radial surface 56 of the wheel 33, it is only necessary to stop the longitudinal motion of the table 12 at a position such that the arm 66 of the dressing apparatus 27 can move normally to bring the diamond 67 downwardly across the radial or end face of the wheel. After this operation is completed, the table 12 moves to the left again, so that the dressing apparatus 27 and the diamond 63 crosses over the surface 57 of the wheel 33 and renews it. Compensation of transverse movement of the wheel 33 for dressing takes place in the control box 45 in the wellknown manner. A similar dress compensation takes place in the control box for energizing the stepping motor 47 which compensates for the fact that a portion of the material of the wheel is removed from the end surface 56 and suitable adjustment must be made in the endwise plunge of the wheel in finishing the radial surface 53 of the workpiece.

We claim:

1. A grinding machine for generating a noncylindrical surface of revolution on a workpiece by the abrasive method, comprising a. a base,

b. a workhead mounted on the base and adapted to support and rotate the workpiece about the axis of the said surface of revolution,

c. a wheelhead mounted on the base and having a rotatable spindle carrying an abrasive wheel,

d. means producing relative movement between the workhead and the wheelhead in directions parallel to the said axis and transversely of the axis to produce a grinding cycle,

e. a dressing apparatus associated with the base and adapted to be held in a fixed position during dressmg,

f. means producing relative movement between the dressing apparatus and the wheelhead both transversely of the axis and longitudinally of the axis to generate a duplicate of the said' surface of revolutionon the surface of the wheel, the means including a master cam, which master cam duplicates a generatrix of the said surface of revolution, and

g. means provided for connecting the master cam to the dressing apparatus and the wheelhead so that the displacement from point to point of the dressing apparatus over the abrasive wheel is substantially less than the corresponding displacement on the master cam, the master cam being moved over 7 a pulse generator and producing pulses proportional in number to the displacement of the surface of the cam from a reference plane, the transverse movement between the dressing apparatus and the wheelhead being brought about by the use of a stepping motor receiving the pulses from the pulse generator.

2. A grinding machine as recited in claim 1, wherein a displacement in the master cam operates through the pulse generator and the stepping motor to produce substantially less displacement between the dressing apparatus and the wheelhead.

3. A grinding machine as recited in claim 2, wherein the dressing apparatus is provided with a secondary dressing element for selectively dressing a radial surface on the abrasive wheel.

4. A grinding machine as recited in claim 3, wherein means is provided for bringing about longitudinal relative motion between the workhead and the wheelhead, which motion consists of large traversing movements and fine feed movements, the feed movements taking place to bring about grinding between the said radial surface of the abrasive wheel and a corresponding radial surface of the workpiece.

5. A grinding machine as recited in claim 4, wherein means is provided to bring about a compensating longitudinal motion operative to compensate for dressing of the said radial surface.

6. A grinding machine as recited in claim 5, wherein a stepping motor operative from electrical pulses brings about the said feeding longitudinal motion and the compensating longitudinal motion.

Claims

1. A grinding machine for generating a non-cylindrical surface of revolution on a workpiece by the abrasive method, comprising a. a base, b. a workhead mounted on the base and adapted to support and rotate the workpiece about the axis of the said surface of revolution, c. a wheelhead mounted on the base and having a rotatable spindle carrying an abrasive wheel, d. means producing relative movement between the workhead and the wheelhead in directions parallel to the said axis and transversely of the axis to produce a grinding cycle, e. a dressing apparatus associated with the base and adapted to be held in a fixed position during dressing, f. means producing relative movement between the dressing apparatus and the wheelhead both transversely of the axis and longitudinally of the axis to generate a duplicate of the said surface of revolution on the surface of the wheel, the means including a master cam, which master cam duplicates a generatrix of the said surface of revolution, and g. means provided for connecting the master cam to the dressing apparatus and the wheelhead so that the displacement from point to point of the dressing apparatus over the abrasive wheel is substantially less than the corresponding displacement on the master cam, the master cam being moved over a pulse generator and producing pulses proportional in number to the displacement of the surface of the cam from a reference plane, the transverse movement between the dressing apparatus and the wheelhead being brought about by the use of a stepping motor receiving the pulses from the pulse generator.